Multi-Hazard Shaking-Tsunami Fatality Risk Estimation for Coastal Communities

Abstract

This study develops a multi-hazard fatality risk model for a coastal community (Tofino) on Vancouver Island, Canada, subjected to earthquake-tsunami threats from the Cascadia subduction megathrust events. The model incorporates variable population distributions and uncertain fatality rate models, in addition to other key model components, such as time-dependent earthquake occurrence, stochastic rupture source, ground motion simulation, and tsunami inundation simulation. Using the developed risk model, exceedance frequency (F) plots in terms of the number of anticipated fatalities (N) are derived for single-hazard and multi-hazard cases. The F-N curves can be used for evaluating the adequacy of current earthquake-tsunami risk situations, compared with the acceptable risk tolerability limits. The obtained F-N curves for Tofino intersect with the local scrutiny line set by the UK Health and Safety Executive, indicating that the earthquake-tsunami risk levels for Tofino residents and visitors fall within the As Low As Reasonably Practicable (ALARP) region. Thereby, when effective risk mitigation measures are available, such actions should be pursued. Moreover, the community-level earthquake-tsunami risk management approach is discussed by considering joint characteristics of fatality and financial risks. The results show very different risk characteristics of the fatality and financial risks due to intense ground motions and tsunami inundations. Such multivariate risk quantification will be essential because more generalized risk management approaches are adopted and implemented across technological and disaster risk domains.